Hydrophobic substrates rendered hydrophilic by coating

ABSTRACT

1. A NORMALLY HYDROPHOBIC SUBSTRATE WHICH HAS BEEN RENDERED HYDROPHILIC BY APPLICATION THEREOVER OF A THIN COATING OF A WATER-SOLUBLE COMPOSITION COMPRISING A WATER-SOLUBLE RUBBERY POLYMER, ALKALINE IN AQUEOUS SOLUTION, CONSISTING ESSENTIALLY OF THE REACTION PRODUCT OF AN EPOXIDIZED WATER-INSOLUBLE NEUTRAL RUBBERY POLYMER SELECTTED FROM THE CLASS CONSISTING OF CIS-1,4-POLYBUTADIENE, BUTADIENE:STYRENE COPOLYMER, BUTADIEN:ACRYLONITRILE COPOLYMER AND CIS-1,4-POLYISOPRENE AND A WATER-SOLUBLE SECONDARY MONO AMINE, SAID EPOXIDIED RUBBERY POLYMER HAVING AN EPOXY EQUIVALENT OF NOT GREATER THAN ABOUT 225.

United States Patent 01 3,843,397 Patented Oct. 22, 1974 3,843,397HYDROPHOBIC SUBSTRATES RENDERED HYDROPHILIC BY COATING Melvin M. Olson,Richfield, Minn., assignor to Minnesota Mining and ManufacturingCompany, St. Paul, Minn. N Drawing. Application Jan. 17, 1972, Ser. No.218,581,

now Patent No. 3,740,414, which is a division of application Ser. No.43,970, June 5, 1970, now Patent No. 3,661,814, which is acontinuation-in-part of application Ser. No. 871,529, Nov. 6, 1969,which in turn is a continuation of application Ser. No. 469,902, July 6,1965, both now abandoned. Divided and this application J an. 19, 1973,Ser. No. 324,960

Int. Cl. C08d /02; C09j 3/00, 3/12 US. Cl. 117-161 UD 7 Claims ABSTRACTOF THE DISCLOSURE A water-soluble rubbery polymer, formed by thereaction of an epoxidized water-insoluble neutral rubbery polymer and awater-soluble secondary mono amine, has particular utility in theformulation of water-soluble pressure-sensitive adhesives and coatingswhich render hydrophobic substrates hydrophilic.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a divisionof copending US. patent application Ser. No. 218,581, filed Jan. 17,1972 and now US. Pat. No. 3,740,414, which application was a division ofSer. No. 43,970, filed June 5, 1970 and now US. Pat. No. 3,661,814,which application was a continuation-inpart of Ser. No. 871,529, filedNov. 6, 1969 and now abandoned, which was, in turn, a continuation ofSer. No. 469,902, filed July 6, 1965, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to novelwater-soluble rubbery polymers and to compositions and products madetherewith.

There has long been a commercial appetite for com positions to primenormally hydrophobic surfaces and render them hydrophilic. By and large,rubbery polymers adhere well to hydrophobic surfaces, but they, too, arehydrophobic and hence not especially receptive to water soluble orhydrophilic coatings.

Definition of Terms As used herein rubbery" means possessing thosephysical parameters (exclusive of solubility) which are used to define arubber as set out in ASTM Standard D 1566- 62T. The appropriate part ofthe definition given therein for rubber reads as follows:

A material that is capable of recovery from large deformations quicklyand forcibly A rubber retracts within one minute to less than 1.5 timesits original length after being stretched at room temperature (20-27"C.) to twice its length and held for one minute before release. All ofthe water-soluble rubbery polymers of this invention meet thiscriterion.

As used herein, water-soluble means requiring l0-30 parts of water todissolve one part of solute; cf. Hackhs Chemical Dictionary, 3rdEdition, McGraw-Hill (1944).

SUMMARY The present invention provides novel hydrophilic rub berypolymers which adhere firmly to both hydrophilic and hydrophobicsurfaces. These polymers, which are actually water-soluble, can also becompounded with tackifiers and used in the manufacture of water-solublenormally tacky and pressure-sensitive adhesives and other compositionshaving unique and valuable properties.

In accordance with the present invention, waterinsoluble neutral rubberypolymers are rendered watersoluble by a comparatively simple two-stepreaction in which a significant number of the double bonds in therubbery material are converted to epoxy groups, and the epoxy groupsthereafter reacted with secondary amine molecules to provide a rubberypolymer characterized by the presence of tertiary amino groups andhydroxyl groups. The resultant polymer is water-soluble, alkaline inaqueous solution, tough and leathery when dry, and still maintains asignificant degree of elasticity. Interestingly, whereas the originalrubbery polymers are soluble in a wide variety of organic solvents(e.g., methylene chloride, dioxane, toluene, benzene, and heptane), themodified water-soluble polymer is essentially insoluble in most organicsolvents. A preferred rubbery polymer for use in preparing materials inaccordance with the present invention is cis-1,4-polybutadiene, thedouble bonds in this polymer being especially susceptible toepoxidation. Other polymers, are useful, however, as will be shown.

That organic solvent-soluble, water-insoluble rubbery polymers can bemade water-soluble and nonpolar solventinsoluble, without detractingfrom their high molecular weight, while still maintaining their rubberycharacteristics to a significant degree, is surprising. Thus, althoughnatural rubber has been wholly or partially epoxidized and thencross-linked with primary amines, the resultant product is less rubbery,and even more water-insoluble than it was before. Secondary amines, ofcourse, are not useful for this crosslinking reaction. Others have alsoreacted 2-methyl-2, 3-epoxy pentane, a model for natural rubber epoxide,with both primary and secondary amines, but there has been no suggestionthat the reaction product is water-soluble, let alone that rubber itselfcould be rendered water-soluble by epoxida'tion and reaction to anappropriate extent with selected secondary amines.

Speaking in general terms, the more double bonds which are epoxidized,the greater the loss in rubbery characteristics sustained by thepolymer. Accordingly, it is generally preferred not to convert allunsaturation to epoxy rings. The requisite degree of epoxidation toobtain watersolubility is dependent upon both the specific rubberypolymer and the specific amine employed. Where the rubbery polymer iscis-1,4-polybu.tadiene, the maximum epoxy equivalent (i.e., molecularweight per epoxy ring) to achieve water-solubility in a subsequentreaction with a secondary amine varies with the water solubility, sterichindrance, etc. of such secondary amines. For example, where the rubberypolymer is cis-1,4polybutadiene and the secondary amine is morpholine,the maximum epoxy equivalent (grams of polymer per epoxy gramequivalent) has been found to be approximately 160. Where the secondaryamine is dimethyl amine, the maximum epoxy equivalent for achievingwater solubility has been found to be approximately 210. It appears thatroughly the same figures apply when rubbery butadienerstyrene copolymersor rubbery butadiene:acrylonitrile copolymers are substituted forpolybutadiene. When dimethylamine is used with polyisoprene, however,the maximum epoxy equivalent approaches 225.

Although a large number of secondary amines show utility in renderingepoxidized rubbery materials watersoluble, several general principles ofselection have proved significant. For example, the greater thewater-solubility of the amine, the more effective it is in renderingepoxidized rubbery polymers water-soluble; hence, infinitelywater-soluble amines are generally preferred. Likewise, the lesssterically hindered the amino nitrogen, the more readily it reacts withan epoxy ring. For example, the presence of side chains or ring units onthe carbon atom adjacent the amino nitrogen is a great deterrent to thereaction. In the absence of steric hindrance, lower molecular weightsecondary amines tend to promote watersol-ubility more effectively thanhigher molecular weight secondary amines, the reaction with epoxy ringsoccurring more rapidly, and the requisite degree of epoxidation of therubbery polymer being lower. The more effective the secondary amine isin promoting water-solubility, the less the degree of epoxidationrequired.

Among the secondary amines which have been found effective in renderingepoxidized rubbery polymers water soluble are dimethylamine,diethylamine, diethanolamine, di n propylamine, di-n-butylamine,di-n-pentylamine, methylbenzylamine, methyl cyclohexylamine,diallylamine, N-methylbenzylamine, N-methylcyclohexylamine,2ethylaminoethanol, morpholine, 2,6-dimethyl morpholine, piperidine,l-methyl piperazine, and pyrrolidine. It will be noted, that theforegoing list includes both saturated and unsaturated straight chainaliphatic compounds cycloaliphatic compounds, and 6-member heterocycliccompounds, and secondary amines in which two different types ofsubstituent are attached to the amino nitrogen. Mixtures of secondaryamines may also be employed to take advantage of their individualproperties. Presence of certain groups in the vicinity of the aminonitrogen apparently inhibits or even prevents, the reaction with epoxygroups. For example, either the direct attachment of a benzene ring tothe nitrogen atom, or branching of an aliphatic substituent within twocarbon atoms of the amino nitrogen seems to prevent reaction with anepoxide ring. Thus, N-methyl aniline, diisopropylamine, anddiisobutylamine all perform more poorly than might be suspected. It isnoted that where the amino nitrogen is included in a heterocyclic ring,there appears to be essentially no problem of steric hindrance.

As previously indicated, water solubility of the finished product isaffected both by the nature of the secondary amine and the degree towhich it reacts with the epoxidized rubbery polymer. Where the polymeris air-1,4- polyhutadiene, and where the secondary amine is morpholine,water solubility ocurs when 1% or more nitrogen is introduced into thepolymer. Where the polymer is polyisoprene and the amine isdimethylamine, water solubility occurs with relatively extendedagitation when only 0.5% nitrogen is present in the polymer. Due to theextended reaction times necessary to both epoxidize and aminizepolyisoprene, the use of this rubber is not favored. Preferably,however, at least about 2 to 3% nitrogen is introduced into the polymer,thereby producing a polymer which is extremely useful in the manufactureof water-soluble normally tacky and pressure-sensitive adhesives. Thepercent nitrogen necessary to achieve water solubility varies with thespecific amine employed; e.g., it will be somewhat lower fordimethylamine and somewhat higher for di-n-butylamine.

DESCRIPTION OF PREFERRED EMBODIMENTS The invention will be betterunderstood by reference to the following specific examples, which arepresented solely for the purpose of illustration.

EXAMPLE 1 Epoxidation of cis-1,4-polybutadiene In a 1-liter, three-neckround bottom flask equipped with stirrer, dropping funnel, thermometer,nitrogen inlet, and reflux condenser, was placed 540 grams (0.5 =mol ofdouble bond) of a 5% solution of 1,4-polybutadiene in toluene. Thepolybutadiene contained approximately 98% cis configuration and had aMooney viscosity (ML 4 at 2120 F.) of about 41. This polymer, asavailable commercially from Goodrich-Gulf Chemicals Incorporated,Cleveland, Ohio, under the trade designation Ameripol CB-220, containingapproximately 1% 2,6- ditertiary butyl p-cresol stabilizer. Into theflask was also placed 6.0 grams of acidic ion-exchange resin (availablecommercially from the Dow Chemical Company under the trade designationas Dowex 50W-X12) which had been leached with acetic acid and dried withsuction on a sintered glass filter, the acetic acid content of thethusdried resin being 17.6%. To the flask was then added 15.4 grams ofglacial acetic acid, making the total amount of acetic acid present0.2738 mol. The mixture was continuously stirred and heated at 60 C. for50 minutes, during which time 37.4 grams (0.55 mol) of 50% hydrogenperoxide was slowly added. Heating and stirring were then continued foran additional 5 hours, at the end of which time the rubber precipitated.The toluene was then poured off and sufficient 1,4-dioxane added todissolve the rubber. The rubber was again precipitated by adding thesolution to methyl alcohol, after which it was re-dissolved in methylenechloride to give an 8.73% solids solution. The epoxy equivalent, on asolids basis, was found to be 137.6 grams per epoxy equivalent,following the procedure outlined by Durbetaki in Anayltical Chemistry,Volume 28 (1956), page 2000.

Epoxidation may, of course, be carried out in a variety of other ways.For example, the ion exchange resin catalyst and the acetic acid mayboth be replaced with formic acid, the time required for reaction beingreduced to approximately minutes, and the reaction temperature requiredbeing 21-24 C. Similarly, the polybutadiene may be dissolved in1,4-dioxane and the hydrogen peroxide replaced with peracetic acid,employing a somewhat longer reaction time. More complete epoxidation maybe obtained by using perphthalic acid, but this oxidizing agent is quiteexpensive, and hence less attractive commercially.

Conversion of epoxidized rubbery polymer to watersoluble polymer In a500 ml., three-neck, round-bottomed flask equipped with stirrer, refluxcondenser and nitrogen inlet was placed 248.5 grams of a 7.86% solutionof epoxidized cis-1,4-polybutadiene in 1,4-dioxane, the epoxy equivalentof the rubber being 112.8 grams per epoxy group (i.e., 56.4% of thetheoretical number of double bonds epoxidized). Next was added 15.2grams (0.174 mol) of morpholine and 1.63 grams (0.0174 mol) of phenol.

It is well known that the amination of oxirane rings can be acceleratedby weak hydrogen donors which serve as catalysts. Phenol and similar lowmolecular weight monohydric alcohols as well as water perform thisfunction. While phenol is generally more active than water, the latteris preferred because it is more easily removed after the reaction iscomplete.

The mixture was stirred and heated on a steam bath for about 18 hours.The reaction mixture was then poured slowly into a large volume ofbenzene in order to precipitate the polymer. The preciiptat ewaspurified by dissolving it in methyl alcohol, re-precipitating inbenzene, and redissolving in methyl alcohol. A water solution of thepolymer could be obtained by adding the methyl alcohol solution to waterand boiling the solution to remove the methyl alcohol and trace amountsof benzene present, yielding a clear water solution. Analysis of thepolymer for percent nitrogen gave a value of 2.63 based on solidpolymer, representing the reaction of 25.4% of the available epoxygroups with morpholine, or conversion of 14.1% of the original linkagesto Use of water-soluble rubbery polymer as primer A conventionalnormally tacky and pressure-sensitive adhesive tape, in which theadhesive was coated over the aluminum vapor-deposited surface of a l-milpolyester film and protected with a removable liner, was backsized with6 grains (solids basis) per 24 square inches of a -12% methyl alcoholsolution of the water-soluble polymer in the preceding section of thisexample. (Although the polymer is miscible with water in allproportions, aqueous solutions tend to be more viscous. Additionally,more volatile solvents permit faster drying.) After evaporation of thesolvent, the resulting thin coating displayed excellent adhesion to thepolyester film surface, in marked contrast to most water-solublematerials. This product was used as a splicing tape in the manufactureof photographic film, the aqueous photographic emulsion displayingexcellent adhesion to the thus-primed surface. In the absence of such acoating, it is found that the photographic emulsion tends to flake offduring drying and contaminate the film in surrounding areas. Thebacksize was essentially tackfree, although it displayed some adhesionfor a slightly moist finger.

Preparation of water-soluble normally tacky and pressure-sensitiveadhesive A 26.9% methyl alcohol solution of the epoxidized cis-1,4-p0lybutadiene:morpholine reaction product described in a precedingsection of this example, was blended with an equal weight (solids basis)of N,N,N'N'-tetrakis (2 hydroxy propyl) ethylene diamine availablecommercially as Quadrol from the Wyandotte Chemical Company. When knifecoated on a 0.003 inch film of biaxially oriented polyethyleneterephthalate, using an aperture of 0.011 inch above the film, and thesolvent then evaporated, the dried adhesive displayed very high webgrab, or initial adhesiveness. The room temperature adhesiveness wasalso measured on a Polyken" ProbeTac-k Tester by forcing the end of astainless steel rod, having a diameter of 5 mm. with an 0.002-inch crownand a surface finish of 5 microinches, against the surface of theadhesive at a rate of 1 cm./ sec. and a pressure of 100 gms./cm. After adwell time of /2 second, the force required to remove the rod at a rateof 1 cm./sec. was measured and found to be 533 grams, which is roughlytwice as great as that for conventional transparent pressure-sensitiveadhesive tape, and about five times as high as for any previously knownwater-soluble pressure-sensitive adhesive.

The internal strength "of the adhesive was measured by placing twoone-half inch strips of the tape in face-toface relationship so thatthey overlapped each other by one-half inch, resulting in a mutualadhesive contact area of one-half inch by one-half inch. The overlappedstrips were then pressed together with a weighted roll and tensioned bythe application of a force of 1000 grams applied between the free endsof the two strips. The time for the face-to-face bond to fail by slidingapart was found to be 7.3 minutes. A shear time of 5 minutes isconsidered adequate for most uses to which transparent tape adhesivesare subjected, and even lower values may be satisfactory where the tapeis not to be subjected to stress in use. Where the tape will besubjected to tensile stresses, as in packaging operations, it is moreimportant to have high internal strength, and times of 30 minutes orhigher before failure are considered desirable.

Double-coated tape made by coating both surfaces of 8-lb. Crystex tissuewith a solution of this adhesive displayed excellent adhesion to almostall surfaces. Because of the adhesive excellent adhesion and watersolubility, tapes of this type offer excellent potential for use as arepulpable splicing tape in paper mills, perhaps even for making highspeed, or flying, splices. A 1% inch square piece of this tape wasplaced between the overlapped ends of two 40-lb. kraft paper strips,rolled once in each direction with a 4 /2 -lb. rubber roller, andallowed to stand for 5 to 10 minutes. When the two ends of the paperwere then clamped, respectively, in the upper and lower jaws of atensile tester, the force required to shear the bond measured at a jawseparation rate of 12 inches per minute was found to be 3.2 lbs.Increasing the nitrogen content of the rubbery polymer tends to decreaseits tackiness but increase its shear strength.

The Quadrol in the composition just described functions as awater-soluble tackifier and plasticizer for the water-soluble modifierrubber. Generally speaking, the tackiness of the adhesive is directlyrelated, and the internal strength inversely related to the amount oftackifier present. Other tackifiers which may be employed includepolyoxyethylene glycol having a molecular weight of 400, polyoxethyleneglycol monophenyl ether, dodecyl aniline, p-n-butoxy phenol, and dodecylphenol. Other plasticizers and tackifiers such as triethanolamine may beemployed. Similarly, antioxidants such as 2,6-di-tert-amyl-phenol may beincluded in the adhesive.

Tabulated below are examples showing the effect of varying the epoxyequivalent of the modified rubbery cis- 1,4-polybutadiene, the secondaryamine employed, and the conditions under which the amine and epoxidizedrubbery polymer are reacted. All polymers are watersoluble. Wherenormally tacky and pressure-sensitive adhesives were made from thepolymers by blending equal weights of water-soluble polymer .andQuadrol, tackiness and internal strength of the adhesives tested asdescribed in the preceding example, are also listed.

EPOXIDI ZED RUBBER:AMINE REACTION M01 M01 Water, Reac- Finished Epoxyratio, ratio, percent tion product Tacki- Interna equivepoxy: phenolwt.0l' Temp., time, adhesive, ness, strength, Example alent Amine amineSolvent amine solution O. hrs. pcrcentN grams min.

110.5 Morpholine 0.6 0.1 20 95 16 1.18 120.8 do 1.0 0.1 10 95 16 1.37 1.0 0. 1 0. 12 88 1. 42 167 33. 6 1.0 0.1 10 26 0.67 0.1 10 95 16 0.67 0.110 95 16 154.8 do 1.0 0.1 10 95 46 114.7 Dimethylamine 1.0 0.1 8.48 9024 134.2 d0 1.0 0.1 0.12 88 24 114.7 Diethylamine 1.0 0.1 8.48 90 241173 Di-n-propylamln 1.0 0.1 10 88 40 Dr-n-butylamine. 1.0 0.1 10 90 90120 Diethanolamine.- 1.0 0.1 10 90 90 123.5 N-methylbenzylamine 1.0 0.110 88 70 120 Pipertdine 1.0 0.1 10 80 20 EXAMPLE 17 A rubbery 76.5 :23.5butadienezstyrene copolymer, having a Mooney viscosity (ML 4 at 212 F.)of 5058, available from Shell Chemical Company, under the tradedesignation GR-S Type 1011 Synthetic Rubber, was epoxidized in the samemanner as described in Example 1, the ultimate epoxy equivalent obtainedbeing 186.1, representing a conversion of approximately 41.5% of thedouble bonds to epoxy groups. The raw rubbery copolymer is somewhatharder to epoxidize to the same degree as cis- 1,4-polybutadiene. Theepoxidized rubber, although less elastic than the original polymer, wasstill tough and, when stretched, slowly returned to its original length.Following the same general procedure outlined in Example 1 (except forthe use of water in the catalyst system and the substitution ofdimethylamine for the morpholine), the epoxidized rubbery copolymer wasreacted with dimethylamine to obtain a water-soluble rubbery copolymer.When blended with an equal weight of Quadrol, the resultant normallytacky and pressure-sensitive adhesive had a tackiness value of 158 andan internal strength of 69.9, when tested as described in Example 1,making it useful as an adhesive for packaging tape.

EXAMPLE 18 A rubbery 80:20 butadienezacrylonitrile copolymer, having aMooney viscosity (ML 4 at 212 F.) of 80, available from GoodrichChemical Company under the trade designation Hycar 1014, was epoxidizedin the same manner as in Example 17 to an epoxy equivalent of 209.1,representing a conversion of approximately 35% of the double bonds inthe original polymer. The raw butadiene2acrylonitrile copolymer is evenharder to epoxidize than the butadienezstyrene copolymer. Although lesselastic than the unmodified polymer, the

epoxidized product was still tough and fairly elastic. The epoxidizedpolymer was then made water-soluble by reacting it with dimethylamine,as in Example 2. When blended with an equal weight of Quadrol, theresultant normally tacky and pressure-sensitive adhesive had a tackinessvalue of 190 and an internal strength of 33.2 when tested as inExample 1. The presence of the polar O group is believed to enhanceafiinity of the adhesive for metal surfaces.

EXAMPLE 19 Cis-1,4-polyisoprene (which has basically the same molecularstructure as natural rubber), having a Mooney viscosity (ML 4 at 212 F.)of 75-95, available commercially from Goodyear Tire & Rubber Companyunder the trade designation Natsyn polyisoprene rubber is epoxidized toan epoxy equivalent of 180 and rendered watersoluble by reaction withdimethylamine. The watersoluble polymer may be employed as a primer forhydrophobic substrates or compounded into an adhesive, as in precedingexamples.

EXAMPLES 20-25 These examples illustrate the rubbery characteristics ofthe water-soluble polymers of this invention and clearly indicate, bycomparison of these characteristics with the characteristics of therubbers before treatment, the sirnilarity in properties. The procedurefor making products of these examples is generally like those used inthe preceding examples with the conditions indicated in the table below,1,4-dioxane being used as the solvent for epoxidized rubber in allcases. It should be noted that while the polyisoprene derivative issoluble, it required a relatively extended period of agitation todissolve completely and form an aqueous solution.

REACTION CONDITIONS FOR EXAMPLES 20-25 Moles of cpoxidation reactantsReaction conditions epoxidation E .0): Double Temp., ezi uiv ExampleRubber Amine Epoxldlzing agent bond Time C. Solvent wt.

20 Cis1,4polybutadiene Dimethyl- Formlc acid plus {0.285 1.83 5 hrs.,-67 Toluene 131 amine. hydrogen perox lde. 2. l9 8 min. plus 1 hr., 27min. 21 do Morpholine -do 1. 33 .....do 65-67 do 124 22 do Piperidlnea0 1. 33 ..do 55-71 .-.do 131 23 (Dis-l, 4 polyiso rene ("Amen DimethylPeracctic acid plus 4.85 0. 936 0. 936 2 hrs., 40 min. 6-22 do 223 ipolSN 600 Mooney visamine. g. anhydrous NaAc. plus 3 hrs., cosity -90). 49min. 24. Butadienezstyrene (GR-S ...do Peracetic acid plus 2.68 0.537 0.5 17 hrs. plus 2 5-22 Methyl- 200 Type 1011). g. anhydrous NaAc. hrs.,ene

min. chorl 25 Butadienemcrylonitrile do Peracetic acid plus 2.5 0. 5 0.5 6 hrs. plus 30 9-30 do 183 (Hyc-ar 1014). g. anhydrous NaAc. min.

Moles of aminatlon reactants Reaction conditions-amination Finishproduct Percent T Moles added iN P conversion emp. equ v. ercent oie 0Example 01 E10 Phenol wt. N to ai in 2 1.2 moles of dimethvlamine wasadded to the mixture after 21 hours,

40 minutes; then heating was continued for 66 hours.

chloride was added to redissolve epoxidized 172 ml. of methanol wasadded to dissolve the polymer after 16 hours,

at which time another 1.0 mole of amine was added.

The water-soluble polymers were prepared for testing by spin castingfrom a methyl alcohol solution of the polymer, using a nitrogen sweep tospeed drying and minimize oxidative attack. Since these polymers areaffected by humidity, the tests were performed in controlled humiditychambers. (The starting rubbers are not so affected and hence weretested in ambient humidity conditions) The testing procedure followedthat given in ASTM Test Procedure D412-64T using an Instron testerexcept that thickness measurements used to determine tensile strengthwere taken at points rather than 3 of the bar portions of thedumbbell-shaped samples. The thickness measurement closest to the breakpoint was used rather than an average thickness as indicated in the ASTMprocedure. The tables below provide a comparison between the baserubbers and their water-soluble counterparts.

films provided with a removable liner), as well as strong butwater-soluble crosslinked adhesives, such as for a repulpable splicingtape useful in paper mills.

Normally tacky and pressure-sensitive adhesives made with thewater-soluble rubber polymers of the present invention display excellentadhesion to a wide variety of materials, and, because such adhesives arealso watersoluble, they stick tenaciously when applied but can beremoved by soaking in water. Adhesives of this type may be employed inthe preparation of Water-activatable labels, thereby making theirapplication simultaneously simple and eifective. Because the modifiedrubbery polymers are essentially inert to most organic solvents,adhesives made with the polymers may be useful for attaching labels tofuel lines, hydraulic fluid lines, cooking oil containers, and the like.The hydrophilic nature of pressure-sensitive PHYSICAL PROPERTIES OF BASERUBBERS Tensile strength in p.s.i.

at various elongations Percent elonge- Percent tion at set at Rubber150% 300% Break break break Remarks AmeripoP' CB 220 (Compare with Ex.-22).... 15 6 12.4 5.86 1, 406 175 Break occurred.

Ameripol SN 600 (Compare with Ex. 23)- 44 3 37.7 33.7 1, 346 312 Do.

GR-S Type 1011 (Compare with Ex. 24). 31 1 28.9 30. 9 1, 838 258 Nobreak occurred at maximum Instron" setting. Hycar 1014 (Compare with Ex.51 4 44.7 41.7 1,738 168 Do.

PHYSICAL PROPERTIES OFWATER-SOLUBLE RUBBERS Tensile strength in p.s.i.Percent at various elongations elonga- Percent Relative on at setExample humidity 150% 300% Break break break Remarks 20 35 137 171 366692 5. 4 Break.

82 89. 7 167 1, 042 26. 5 D0. 21 38 57. 6 65. 8 101 1, 366 43. 7 Do.

44. 3 45. 3 61.1 942 35. 4 D0. 22 35 94. 6 102 137 1, 308 53. 6 Do.

50 63.7 60.9 1, 800 No break at maximum Instron setting. 23 35 127 189867 687 3.1 Break.

50 107 147 622 666 4. 6 Do 24 35 1, 270 1, 710 1, 745 325 22. 6 Do.

50 135 189 290 567 10. 9 D0 25 33 36. 4 40. 5 114. 2 1, 450 181 No breakvalues given at maximum "Instron" extension.

""""" 25. 8 25. 8 27. 9 60. 2 1, 517 204 Brea The man skilled in the artwill recognize that it is not feasible to set forth all the variationsto which this invention is susceptible, and many modifications willreadily suggest themselves. For example, the higher the molecular weightof the rubbery polymer, the greater the number of tertiary amino groupsrequired to induce an equivalent degree of water-solubility. Likewise,the water-solubilizing ability of a given secondary amine is enhanced ifthe amine compound also contains OH or other polar groups. Where it isdesired to have a polymer which is water-soluble but which can becross-linked to an insoluble state, it is possible to introducecompounds which react with either two or more epoxy rings or two or morehydroxyl groups under the stimulus of, e.g., heat. For example,dihalogen compounds such as ethylene dichloride, dichloromethyl ether,and a,w-dichloropolyoxyethyleue may react with the tertiary aminogroups, thereby forming water-soluble crosslinking salt bonds. The rateof crosslinking may be suitably controlled by selected dihalogencompounds having the desired degree of reactivity. Where desired, thesecompounds may be enclosed in capsules which rupture under apredetermined threshold stimulus of heat or pressure. Crosslinking maybe similarly effected through the OH groups, using glyoxal or aformaldehyde donor such as hexamethylene tetramine. Such adhesivecompositions lend themselves to the preparation of self-sustainingthermosetting pressure-sensitive adhesive transfer tapes (i.e., tackybut curable adhesive adhesives of the type described herein also reducesstatic electricity problems which plague the users of many conventionaltape products and may eliminate the need for antistatic backsizes inmost situations. The electrical conductivity of these adhesives alsosuggests their use for holding electrodes in place inelectrocardiographic work. Both the conductivity and the bacteriostaticproperties of the adhesive maybe enhanced by reacting it with methylbromide to form quaternary salts.

I claim:

1. A normally hydrophobic substrate which has been rendered hydrophilicby application thereover of a thin coating of a water-solublecomposition comprising a water-soluble rubbery polymer, alkaline inaqueous solution, consisting essentially of the reaction product of anepoxidized water-insoluble neutral rubbery polymer selected from theclass consisting of cis-1,4-polybutadiene, butadiene:styrene copolymer,butadiene:acrylonitrile copolymer and cis-1,4-polyisoprene and awater-soluble secondary mono amine, said epoxidized rubbery polymerhaving an epoxy equivalent of not greater than about 225.

2. The substrate of Claim 1 wherein the neutral rubbery polymer iscis-1,4-p0lybutadiene.

3. The substrate of Claim 1 wherein the neutral rubbery polymer is abutadiene:styrene copolymer.

4. The substrate of Claim 1 wherein the neutral rubbery polymer is abutadiene:acrylonitrile copolymer.

5. The substrate of Claim 1 wherein the neutral rubbery polymer iscis-1,4 polyisoprene.

6. The substrate of Claim 1 wherein the secondary mono amine ismorpholine.

7. The substrate of Claim 1 wheerin the secondary mono amine is dimethylamine.

References Cited UNITED 12 2,927,100 3/1960 Canterino 260--83.32,781,335 2/1957 Culpery 260-85.7 2,660,563 11/1953 Banes 260--94.7 X

5 LEON D. ROSDOL, Primary Examiner D. L. ALBRECHT, Assistant ExaminerSTATES PATENTS Olson 260-326 A Olson 26083.3 10 117-122 PA, 138.8 A,138.8 F, 161 UH, 161 ZB; lgng 26029.2 156-327, 330, 334; 26032.6A

ams.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.1131137397 Dated nM- 99 1 0711 Inventor(s) Melvin M. Olson It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 3, line 69, "2120 F." should be 212F.

Column l, line 53, "preciiptat" should be precipitate Column 11, Claim7, line 1', "wheerin" should be wherein Signed and sealed this 22nd dayof ezpril 1975.

T 025 Commissioner of Patents hu 1 be slam.) m Attestim: Gfficer andTrademarks I FORM PO- 050 (1- uscoMM-oc 60376-P69 i UTS. GOVIIIII"'IIITIIG OFFICE ll" O-IC'SM

1. A NORMALLY HYDROPHOBIC SUBSTRATE WHICH HAS BEEN RENDERED HYDROPHILICBY APPLICATION THEREOVER OF A THIN COATING OF A WATER-SOLUBLECOMPOSITION COMPRISING A WATER-SOLUBLE RUBBERY POLYMER, ALKALINE INAQUEOUS SOLUTION, CONSISTING ESSENTIALLY OF THE REACTION PRODUCT OF ANEPOXIDIZED WATER-INSOLUBLE NEUTRAL RUBBERY POLYMER SELECTTED FROM THECLASS CONSISTING OF CIS-1,4-POLYBUTADIENE, BUTADIENE:STYRENE COPOLYMER,BUTADIEN:ACRYLONITRILE COPOLYMER AND CIS-1,4-POLYISOPRENE AND AWATER-SOLUBLE SECONDARY MONO AMINE, SAID EPOXIDIED RUBBERY POLYMERHAVING AN EPOXY EQUIVALENT OF NOT GREATER THAN ABOUT 225.